U.S. patent application number 10/354300 was filed with the patent office on 2003-06-19 for method and device for testing a sample of fresh whole blood.
Invention is credited to Baugh, Robert F., Johnston-Eaton, Julie S., Lutz, Colleen.
Application Number | 20030113929 10/354300 |
Document ID | / |
Family ID | 24237952 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030113929 |
Kind Code |
A1 |
Baugh, Robert F. ; et
al. |
June 19, 2003 |
Method and device for testing a sample of fresh whole blood
Abstract
A method and device for testing a sample of fresh whole blood.
In particular the present invention provides a method and device
for testing a sample of fresh whole blood to determine whether a
patient would benefit from the administration of a blood factor
(such as AT III.)
Inventors: |
Baugh, Robert F.; (Parker,
CO) ; Johnston-Eaton, Julie S.; (Conifer, CO)
; Lutz, Colleen; (Plymouth, MN) |
Correspondence
Address: |
MEDTRONIC, INC.
710 MEDTRONIC PARKWAY NE
MS-LC340
MINNEAPOLIS
MN
55432-5604
US
|
Family ID: |
24237952 |
Appl. No.: |
10/354300 |
Filed: |
January 30, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10354300 |
Jan 30, 2003 |
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09560470 |
Apr 28, 2000 |
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6541262 |
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Current U.S.
Class: |
436/69 ; 422/73;
435/13 |
Current CPC
Class: |
G01N 33/86 20130101 |
Class at
Publication: |
436/69 ; 435/13;
422/73 |
International
Class: |
G01N 033/86 |
Claims
What is claimed is:
1. A method for determining the response of a sample of a patient's
whole blood to heparin in the presence and absence of supplemental
antithrombin III comprising the steps of: providing a first
channel; providing a second channel with a primary reagent;
providing a third channel with the primary reagent and a secondary
reagent; adding a first amount of fresh whole blood to the first
channel; adding a second amount of fresh whole blood to the second
channel; adding a third amount of fresh whole blood to the third
channel; and determining the time required for a clot to be formed
in the first, second and third channels.
2. The method according to claim 1 further comprising the step of
mixing the first amount of fresh whole blood added to the first
channel.
3. The method according to claim 1 further comprising the step of
mixing together in the second channel the primary reagent and the
second amount of fresh whole blood added to second channel.
4. The method according to claim 3 wherein step of providing the
second channel with a primary reagent further comprising provide
the primary reagent in a first concentration.
5. The method according to claim 1 further comprising the step of
mixing together in the third channel the primary reagent, the
secondary reagent and the third amount of fresh whole blood added
to third channel.
6. The method according to claim 1 wherein the step of determining
the time required for a clot to be formed in the first, second and
third channels further comprising mixing the first amount of fresh
whole blood added to the first channel, mixing together in the
second channel the primary reagent and the second amount of fresh
whole blood added to second channel, mixing together in the third
channel the primary reagent, the secondary reagent and the third
amount of fresh whole blood added to third channel and sensing the
presence of a clot in each of the first, second and third
channels.
7. The method according to claim 1 wherein the step of providing a
second channel with a primary reagent further comprising providing
a second channel with heparin
8. The method according to claim 7 wherein the step of providing a
second channel with heparin further comprising the step of
providing a second channel with heparin in the amount of between
approximately 0.1-10.0 Units/ml
9. The method according to claim 8 wherein the step of providing a
second channel with heparin in the amount of between approximately
0.1-10.0 Units/ml further comprising the step of providing a second
channel with heparin in the amount of approximately 2.5
Units/ml.
10. The method according to claim 1 wherein the step of providing a
third channel with the primary reagent and a secondary reagent
further comprising providing a third channel with AT III
11. The method according to claim 10 wherein the step of providing
a third channel with AT III further comprising providing a third
channel with AT III in the amount of between approximately 0.1-10.0
Units/ml
12. The method according to claim 11 wherein the step of providing
a third channel with AT III in the amount of between approximately
0.1-10.0 Units/ml further comprising providing a third channel with
AT III in the amount of approximately 0.8 Units/ml.
13. A cartridge adapted to receive sample of blood to be tested for
the blood clotting time comprising: a housing having a first
channel, second channel and a third channel; wherein first channel
has a primary reagent and a mechanical mixer a adapted to mix the
primary reagent with any blood which is received within the first
channel wherein second channel has a primary reagent and a
secondary reagent and a mechanical mixer b adapted to mix the
primary reagent and the secondary reagent with any blood which is
received within the second channel.
14. A cartridge according to claim 13 further comprising third
channel has a mechanical mixer C adapted to mix any blood which is
received within the third channel.
15. A cartridge according to claim 14 wherein the mechanical mixers
A, B and C are each fashioned to move in a linear manner through
each respective channels.
16. A cartridge according to claim 13 further comprising first
channel has first A chamber and a second A chamber, the first A
chamber containing the primary reagent and the second chamber
containing a solution.
17. A cartridge according to claim 16 wherein the mechanical mixer
A is disposed to separate the first A chamber from the second A
chamber when the mechanical mixer is in a first position,
18. A cartridge according to claim 13 further comprising second
channel has first B chamber and a second B chamber, the first B
chamber containing the primary reagent and the secondary reagent;
the second chamber containing a solution.
19. A cartridge according to any of claims 13-18 wherein the
primary reagent is heparin
20. A cartridge according to any of claims 13-18 wherein the
secondary reagent is AT III
21. A cartridge according to any of claims 13-18 wherein the first
reagent is heparin in the amount of between approximately 0.1-10.0
Units/ml
22. A cartridge according to claim 21 wherein the first reagent is
heparin in the amount of approximately 2.5 Units/ml.
23. A cartridge according to any of claims 13-18 wherein the
secondary reagent is AT III in the amount of between approximately
0.1-10.0 Units/ml
24. A cartridge according to claim 23 wherein the secondary reagent
is AT III in the amount of approximately 0.8 Units/ml.
Description
FIELD OF THE INVENTION
[0001] The management of hemostasis (also known as blood clotting)
is an important requirement for a successful surgery. The exposure
of blood to foreign surfaces, which often occurs during surgery, as
well as the surgery itself can induce the activation of the
clotting mechanism.
[0002] The clotting mechanism can be mediated in a variety of ways.
One of the more common methods of mediating coagulation is to
administer heparin.
[0003] The administration of heparin, however, must be done
carefully. Care is required because the response of any one patient
to a particular dose of heparin is highly variable, depending upon
the particular physiology of each patient. Thus, it is often quite
necessary for physicians or other care givers to understand the
exact blood physiology of a patient such that a proper heparin
dosage may be administered.
[0004] The Medtronic HMS Plus.TM. hemostasis management system may
be used to measure many blood parameters, including activated
clotting time (ACT). The Medtronic HMS Plus.TM. system uses an ACT
to measure a heparin dose response methodology. The heparin dose
response curve may be seen in FIG. 1.
[0005] The heparin dose response requires a small sample of whole
blood from a patient. The whole blood is introduced into particular
assay channels or vials, at least one (and preferably two) of the
assay vials having no heparin reagent, at least one (and preferably
two) more assay vials having a heparin reagent concentration of A
and at least one (and preferably two) more assay vials having a
heparin reagent concentration of B, where the concentration denoted
as A is different from the concentration denoted as B.
[0006] The test begins by introducing the same volume of blood into
each of the channels or vials. Thereafter the blood is mixed
(preferably using a plunger.) The blood clots in each of the
channels or vials at differing times. The clot is measured by
timing the descent rate of the plunger. Ultimately, the clotting of
each of the vials or channels may graphed as shown in FIG. 1, where
line 1 may be draw through the three data points created by the
formation of a blood clot in each channel or vial. That is, blood
without any reagents (depicted here as data point DP.sub.O), blood
with heparin reagent concentration A (depicted here as data point
DP.sub.A) and blood with heparin reagent concentration B (depicted
here as data point DP.sub.B). As seen, the heparin dose response is
a linear function when the ACT is used to initiate coagulation.
[0007] The heparin dose response line varies from patient to
patient. That is, the linear heparin dose response seen in FIG. 1
has differing slopes for differing patients. Patients may have a
heparin dose response line having slopes such as those seen as line
1' (very low slope) or line 1" (very high slope.) Generally
speaking, the flatter or lower the slope of the line the more
heparin resistant the patient is. Heparin resistant patients may
have a variety of factors at work accounting for the heparin
resistance. For example, these patients may have mechanisms which
complex or bind the heparin, not allowing the heparin to inhibit
blood coagulation. There may also be mechanisms present in the
patient that rapidly eliminate the heparin. Finally, these patients
may be heparin resistant due to their levels of the serine protease
inhibitor antithrombin III (AT III). Heparin is a catalyst, that
is, it helps prevent coagulation by accelerating the natural
anticoagulant mechanisms present in the patient. The primary
mechanism is the inhibition of thrombin, the primary protease of
blood coagulation, by AT III. Without adequate amounts of AT III,
heparin is ineffective in prevent blood coagulation.
[0008] AT III targets proteases of the coagulation cascade, and in
particular thrombin. Heparin accelerates the rate with which AT III
inhibits the proteases. Thus, without the presence of ACT III, the
anticoagulant activity of heparin is severely diminished. The
differences in which individuals respond to heparin may be affected
by the differences in their AT III levels. Thus, a goal of the
present system is to provide a method of assessing the heparin dose
response while further accessing whether such heparin dose response
is attributable to presence or absence of sufficient levels of AT
III within the patient.
[0009] Thus there exists a need for a method and device which may
reliably sense the heparin dose response of fresh whole blood as
well as whether the fresh whole blood (and thus patient) has, or
requires additional, AT III.
SUMMARY OF THE INVENTION
[0010] The present invention provides a method and device for
testing a sample of fresh whole blood. In particular the present
invention provides a method and device for testing a sample of
fresh whole blood to determine whether a patient would benefit from
the administration of a blood factor (such as AT III.) Patients may
benefit from such an administration both prior to surgery as well
as for other reasons, such as if a patient suffers from acute
myocardial ischemia. The blood factor may be a factor which is
involved with the coagulation cascade. In the preferred embodiment
the blood factor is the serine protease inhibitor Antithrombin III
(AT III). The method of the present invention determines whether a
patient would benefit from the administration of a blood factor
prior to surgery through the testing of a whole blood sample within
at least three testing channels, a first channel, a second channel
and a third channel. Preferably the at least three channels are
provided within an integral cartridge. The first channel is a
control channel and contains a portion of a single whole blood
sample without any additives. The second channel contains a portion
of the single whole blood sample along with a
thrombotic/hemorrhagic agent. The third channel contains a portion
of a the single whole blood sample along with the
thrombotic/hemorrhagic agent and a blood factor which is involved
in controlling the coagulation cascade. In the preferred embodiment
the thrombotic/hemorrhagic agent which may be selected from
glycosaminoglycans which have the anticoagulant sequence which
binds to the blood factor which is involved in controlling the
coagulation cascade. In the preferred embodiment the
thrombotic/hemorrhagic agent is heparin and the blood factor which
is involved in controlling the coagulation cascade is AT III. Each
channel is provided with a device for assessing when a clot is
formed. The time for the formation of a clot in each channel may be
used to determine whether the patient would benefit from the
administration of a blood factor prior to surgery. In the preferred
embodiment the method may be performed within the Medtronic Hepcon
HMS Plus.TM. Hemostasis Management System. The device of the
present invention may be practiced through a test cartridge used
within the Medtronic Hepcon HMS Plus.TM. Hemostasis Management
System but modified to contain the appropriate reagents, identified
above, in the testing cartridges.
[0011] The present invention, furthermore, is advantageous, as it
performs such tests on a sample of fresh whole blood, as opposed to
citrated blood. The use of fresh whole blood as opposed to citrated
blood is generally preferred, since the inclusion of citrate into
blood affects blood characteristics, and thus the test. In
particular, citrate causes platelets to activate. Over time,
moreover, citrate itself affects clotting. Both of these affects
may lead to misleading test results, possible affecting patient
care. In view of these deficiencies with citrated blood, past
efforts have been made to compensate or mediate the affects of
citrate in blood. See, for example, Baugh et al. U.S. Pat. No.
4,871,677 "Method Of Collecting And Analyzing A Sample Of Blood
When Monitoring Heparin Therapy." Such past efforts, while of some
benefit, have not met with ideal results.
BRIEF DESCRITPTION FO THE FIGURES
[0012] FIG. 1 is a graph for the clotting time of blood plotted
against at least two levels of heparin, otherwise know as a heparin
response curve according to the prior art.
[0013] FIG. 2 is a graph for the clotting time of a sample of blood
in which the heparin dose response is determined while the blood is
provided with at least one level of a reagent that affect the
anticoagulant activity of heparin.
[0014] FIG. 3 is a perspective view of the Medtronic HMS Plus.TM.
instrument within which a test or assay cartridge may be used.
[0015] FIG. 4 is a top plan view of a test or assay cartridge 501
used with the instrument shown in FIG. 3 within which the present
invention may be used.
[0016] FIG. 5 is a side plan view of the cartridge 501 shown in
FIG. 4.
[0017] FIG. 6 depicts a method of determining whether a patient
would benefit from the administration of a blood factor.
[0018] The FIGS are not necessarily to scale.
DETAILED DESCRIPTION OF THE FIGURES
[0019] FIG. 1 is a graph for the clotting time of blood plotted
against at least two levels of heparin, otherwise know as a heparin
dose response curve according to the prior art. As discussed above,
such a graph may be created through the Medtronic HDR.TM. assay
performed in the Medtronic HMS Plus.TM. Hemostasis Management
System automated testing device. As known, such a test is used to
test the response of a fresh, whole blood sample to a variety of
heparin doses. As seen, at least three data points, are collected,
depicted here as DP-0, DP-A and DP-B.
[0020] The present invention takes advantage of the excess
capability found in the current known Medtronic HMS Plus.TM.
Hemostasis Management System, three data channels are used, while
only two should actually be needed to ascertain the linear heparin
dose response, and uses this excess channel capacity to
concurrently create data of a heparin response with an additional
amount of a blood factor which is involved with the coagulation
cascade. Through such a system, data may be concurrently collected
to both adjudge the heparin dose response, as well as the effect on
such response to the addition of an added blood factor which is
involved with the coagulation cascade. A graph which may be created
with this invention is shown in FIG. 2.
[0021] FIG. 2 is a graph for the clotting time of a sample of blood
in which the heparin dose response is determined while the blood is
provided with at least one level of a reagent that affects the
anticoagulant activity of heparin with a known amount of heparin.
As seen, BL represents a baseline data point depicting the time
required for a sample of fresh whole blood to clot in a specified
channel or vial. Specific details of the channel or vial are
described below. DD-1 represents a data point depicting the time
required for a sample of fresh whole blood to clot in a specified
channel or vial in the presence of a specified amount of heparin.
DD-2 represents a data point depicting the time required for a
sample of fresh whole blood to clot in a specified channel or vial
in the presence of a specified amount of heparin and also in the
presence of a blood factor that is involved with the coagulation
cascade. In the preferred embodiment, this blood factor is AT III.
While in this depiction the data point DD-2 is shown as above DD-1,
the specific relationship between these data points will vary from
patient to patient. In fact, it is this patient to patient
variation which is the heretofore unmet need which the present
invention meets.
[0022] FIG. 3 is a perspective view of the Medtronic HMS Plus.TM.
instrument within which a test or assay cartridge may be used. The
Hepcon HMS Plus is a microprocessor based, multi-channel clot
timing instrument with automated syringe handling for pipetting
blood into single use cartridges. It performs in vitro blood
evaluations including heparin sensitivity evaluations, heparin
assays, activated clotting times, and platelet function
evaluations. As seen the Hepcon HMS Plus instrument includes a
sample dispenser/syringe 1, a start/stop key 2, a carry handle 3, a
printer 4, main keypad 5, LCD screen and keys 6, heat block and
cartridge receiver 7, and a protective shield 8. The Hepcon HMS
Plus instrument is available from Medtronic Inc., Minneapolis,
Minn.
[0023] FIG. 4 is a-top plan view of a test or assay cartridge 501
used with the instrument shown in FIG. 3 within which the present
invention may be used. As seen the cartridge 501 includes a
plurality of channels 502-507. Positioned upon the top of housing
is an optical code 508. The purpose of the optical codes is to let
the HMS Plus.TM. instrument detect (via the software) what type of
assay is being performed. Since there are a number of different
assays which may be performed on the instrument, it is required
which type of assay is to be performed so that the clotting data
can be analyzed correctly. Of course a variety of other schemes
could be used, as opposed to optical codes, such as user-input,
magnetic, EEPROM, reflective or bar code.
[0024] FIG. 5 is a side plan view of the cartridge 501 shown in
FIG. 4. As seen, each channel 502 contains a plunger 519. Plunger
519, extends above the upper surface of housing so as to be able to
be actuated, upwardly and downwardly, by a testing device, such as
the Medtronic HMS Plus.TM., discussed above. As further seen
plunger 519, features plunger flag 520 along the upper portion.
Plunger shaft 521 continues downwardly to daisy plug 523. Defined
between daisy plug 523 and bottom plug 525 is reagent chamber 524.
Thus, daisy plug 523 defines above it an upper reaction chamber
522, within which fresh whole blood is added, while daisy plug 523
defines below it the reagent chamber 524. As can be appreciated,
movement of the plunger, and then the plunger daisy, upward removes
the daisy plug from its position as shown and allows fluids within
the reaction chamber 522 and reagent chamber 524 to mix.
[0025] As discussed above, the test of the current invention is
carried out using a cartridge having a series of at least three
separate channels. In the preferred embodiment, each channel is
repeated at least once so that three channels, each repeated once,
means six channels may be used. Each channel is constructed the
same as that described above, although the compounds within the
reaction and reagent chambers for each channel may vary (Further
details may be found in U.S. Pat. No. 5,951,951, incorporated
herein by reference).
[0026] In the preferred embodiment, the first channel chamber does
not have, within the reaction chamber, any reagents. In the first
channel reagent chamber, however, a solution is provided to promote
contact activated coagulation. This is provided so as to accelerate
coagulation because without such a compound the time required for a
clot to form would be extensive
[0027] In the second channel, the reagent chamber features, like
the first channel, a solution to promote contact activated
coagulation The reaction chamber further has positioned within a
primary reagent, such as a primary reagent to inhibit blood
coagulation, preferably heparin. Preferably the heparin is provided
in the amount of between approximately 0.1-10.0 Units/ml, and
preferably in the amount to give a sample concentration of
approximately 2.5 Units/ml. In the preferred embodiment, this
heparin is provided in a dried form, dried to the inner surface of
the reaction chamber such that it is dissolved upon contact with
the fresh whole blood sample.
[0028] In the third channel, the reagent chamber features, like the
first channel and the second channel, a solution to promote contact
activated coagulation. The reaction chamber of the third channel
further has positioned within a primary reagent, such as a primary
reagent to inhibit blood coagulation, preferably heparin.
Preferably the heparin is provided in the amount of between
approximately 0.1-10.0 Units/ml, and preferably in the amount to
give a sample concentration of approximately 2.5 Units/ml. In the
preferred embodiment, this heparin is provided in a dried form,
dried to the inner surface of the chamber such that it is dissolved
upon contact with the fresh whole blood sample. The third channel
further features, a blood factor which is involved with the
coagulation cascade, and preferably a blood factor which targets
proteases of the coagulation cascade, and in particular thrombin.
In the preferred embodiment, this blood factor is AT III provided
in the amount to give a sample concentration of between
approximately 0.1-10.0 Units/ml, and preferably in the amount of
approximately 0.8 Units/ml. In the preferred embodiment, this AT
III is also provided in a dried form, dried to the inner surface of
the reaction chamber such that it is dissolved upon contact with
the fresh whole blood sample.
1 TABLE ONE Channel Reagent chamber Reaction chamber First channel
12% kaolin in a -- buffered isotonic saline solution Second channel
12% kaolin in a 2.5 Units/ml Heparin buffered isotonic saline
solution Third channel 12% kaolin in a 2.5 Units/ml Heparin
buffered isotonic 0.8 U/ml AT III saline solution
[0029] In use, it is important to note the order in which the
channels are filled with sampled blood. Channels which contain
anticoagulant are pipetted first and those which do not contain
anticoagulant are filled last. This order or sequence prevents some
premature activation of the baseline sample in the cartridge. That
is, otherwise blood would be activated by the cartridge body while
the other channels having coagulate were being filled. Even though
the total time required for such fill is small, the effect on the
blood and the test results is to be avoided.
[0030] The present invention further encompasses a method of
determining whether a patient would benefit from the administration
of a blood factor. Such a method is depicted in FIG. 6. At 601 a
sample of fresh whole blood is taken from a patient. At 602 a whole
blood testing assay cartridge is provided, the cartridge having at
least three testing channel. The cartridge is preferably
constructed as described above with regards to FIG. 4. At 603, the
cartridge is placed into the instrument. At 604, the instrument
automatically introduces the sample into the assay cartridge. At
605 the instrument actuates the cartridge and begins testing for
clot formation in the cartridge channels. The device operates to
both mix the blood in each channel, preferably through the upward
and downward movement of the plunger, as well as to sense the
formation and presence of a blood clot. Next, at 606, the formation
of a blood clot and its time of detection are sensed and noted for
each of the first channel, second channel and the third channel.
The times for each clot formation in each channel may thereafter be
used to determine whether a patient would benefit from the
administration of a blood factor prior to surgery. It should be
noted, incidentally, that the instrument does not actually supply a
plot of the resulting information, but rather merely computes the
slope of the responses. The graph essentially illustrates what the
instrument is doing via mathematical calculations. The comparison
of the slopes, moreover, is made by the instrument and if the slope
increases by more than 20%, the instrument gives an-indication that
the addition of AT III will be beneficial.
[0031] Although a specific embodiment of the invention has been
disclosed, this is done for purposes of illustration and is not
intended to be limiting with regard to the scope of the invention.
It is contemplated various substitutions, alterations and/or
modifications may be made to the disclosed embodiment without
departing from the spirit and scope of the invention. Such
modifications may include substituting elements or components which
perform substantially the same function in substantially the same
way to achieve substantially the same result for those described
herein.
* * * * *